The invention relates to a magnetic recording hard disk drive (HDD). More specifically, the invention relates to a hybrid surface format HDD including a shingled magnetic recording (SMR) surface and a random block overwrite (RBO) surface.
An HDD formatted principally for SMR employs an SMR formatted write head that writes magnetic transitions by making a plurality of consecutive circular paths that partially overlap. A region of adjacent tracks is written so as to overlap one or more previously written tracks. The shingled tracks must be written in sequence. Non-overlapped portions of adjacent paths form the shingled data tracks, which are narrower than the width of the write head. The narrower shingled data tracks allow for increased data density. Once written in shingled structure, an individual track cannot be updated in place because that would overwrite and destroy data in the overlapping tracks. In contrast, a disk drive formatted for RBO allows random block overwrite without disturbing existing data.
Shingle written data tracks provide a high track density. However, shingled written data tracks do not allow random block overwrite. In order to overwrite a data block in the shingled data track, a significant portion of the disk must be erased while writing is taking place.